This invention is generally relative to wireless outdoor handheld ultra wideband communications.
On Apr. 22, 2002, U.S. Federal Communications Commission (FCC) released the revision of Part 15 of the Commission's rules regarding ultra-wideband (UWB) transmission systems to permit the marketing and operation of certain types of new products incorporating UWB technology. With appropriate technology, UWB device can operate using spectrum occupied by existing radio service without causing interference, thereby permitting scarce spectrum resources to be used more efficiently. It has been known that UWB technology offers significant benefits for Government, public safety, businesses and consumers under an unlicensed basis of operation spectrum.
UWB devices can be classified in three types based on the operating restrictions: (1) imaging system including ground penetrating radars and wall, through-wall, surveillance, and medical imaging device, (2) vehicular radar systems, and (3) communications and measurement systems. In general, FCC is adapting unwanted emission limits for UWB devices that are significantly more stringent than those imposed on other Part 15 devices. In other words, FCC limits outdoor use of UWB devices to imaging systems, vehicular radar systems and handheld devices. Limiting the frequency band, which is based on the −10 dB bandwidth of the UWB emission, within certain UWB products will be permitted to operate.
The outdoor handheld UWB systems are intended to operate in a peer-to-peer mode without restriction on location. The handheld UWB device must operate in the frequency band from 3.1 GHz to 10.6 GHz, with an extremely conservative out of band emission mask to address interference with other devices. The handheld UWB devices are permitted to emit at or below the Part 15.209 limit in the frequency band below 960 MHz. The emissions above 960 MHz must conform to the following emissions mask as shown in Table 1:
TABLE 1Frequency (MHz)EIRP (dBm) 0-960−41.3 960-1610−75.31610-1900−63.31900-3100−61.3 3100-10600−41.3Above 10600−61.3
FCC proposed to define a UWB device as any device where the fractional bandwidth is greater than 0.25 based on the formula as follows:
                              FB          =                      2            ⁢                          (                                                                    f                    H                                    -                                      f                    L                                                                                        f                    H                                    +                                      f                    L                                                              )                                      ,                            (        1        )            where fH is the upper frequency of the −10 dB emission point and fL is the lower frequency of the −10 dB emission point. The center frequency of the UWB transmission is defined as the average of the upper and lower −10 dB points as follows:
                              F          c                =                                                            f                H                            +                              f                L                                      2                    .                                    (        2        )            In addition, a minimum frequency bandwidth of 500 MHz must be used for an UWB device regardless of center frequency.
Given an entire frequency bandwidth of 7.5 GHz (3.1-10.6 GHz), it is difficult to design a transmitter and/or receiver device for a single UWB signal that occupies the entire frequency bandwidth from 3.1 GHz to 10.6 GHz directly. This is because we need to have a very-high speed A/D and D/A converter as well as a high-speed circuit and digital signal processor to operate an UWB device for the wireless communications. As a result, the cost of the UWB device could be expense. In addition, interference between the UWB and other devices, such as a WLAN 802.11a device, can occur because the WLAN 802.11a device operates in the lower frequency range from 5.15 GHz to 5.35 GHz or in the upper frequency range from 5.725 GHz to 5.825 GHz. Moreover, the UWB device may not be able to transmit data with scalability.
Due to the proliferation of 7.5 GHz UWB for wireless broadband communications, it would be desirable to have a new technology of developing one multichannel UWB solution with a scalability of the transmission data rate, which not only reduces the interference with WLAN 802.11a devices but also has a lower cost for an outdoor handheld UWB transceiver. The multichannel UWB solution highly depends on a multichannel filter, which must meet the FCC request of the outdoor emission limitation, to provide the multichannel-based multi-carrier modulation. Therefore, in this embodiment, the multichannel filter-based outdoor handheld ultra wideband communications is invented for wireless broadband communications.
Thus, there is a continuing need of the multichannel filter-based outdoor handheld UWB transceivers that enables a user to transmit the data rate with programmability and scalability and avoid the interference with WLAN 802.11a devices.